In the U.S. Pat. No. 4,121,584 of Turner, et al. a new technique for the positive control of flow of parenteral solution or the like is provided, utilizing only the gravity head pressure of the solution, coupled with excellent accuracy of delivery volume. The flow control device utilizes a pair of alternating valves which open and close, controlling the inlet and outlet to a metering chamber.
In the patent application of Nicholas Zissimopoulos Ser. No. 878,970, filed Feb. 17, 1978 an E-frame electromagnet switch is provided which gives improved characteristics of control and convenience to the previously described invention. This electromagnetic switch includes an E-frame electromagnet which controls an armature having magnets on the ends thereof. According to the polarity of the E-frame electromagnet, the armature pivots back and forth between a pair of first and second pivotal positions opening and closing the inlet and outlet valves of a flow controller device, which may be generally similar to the Turner, et al. arrangement.
In this invention, further improvements are provided in that the switching device of this invention operates very quietly to avoid disturbing the patient, for example, and at the same time the life of the magnet means used in the device is prolonged by being protected from shock. Accordingly, a substantial improvement in the design of the device of this invention is achieved.